Not applicable.
Not applicable.
This invention relates to video image processing, and more particularly, to a method of searching recorded video images to quickly locate areas of activity recorded on the video.
In video recording systems, for example those used for surveillance of a premises, a camera obtains a series of video images of a scene. These images are processed by an image processing system and the results stored in a digital video recorder (DVR) or the like. The images are stored sequentially; i.e., the first image obtained first, the second image obtained second, and so forth. The images are usually digitally converted analog signals, and these digital images are stored in a computer memory or on a disc. Most surveillance systems are used at times when little activity is expected within the scene viewed by the camera. Accordingly, the recorded video will typically have lengthy segments where there is no change in the recorded image or there may be small changes due to environmental disturbances such as video monitor screen savers, oscillating fans, or any of a number of other disturbances.
A drawback in conventional recording systems, is that in order to view segments of the video in which xe2x80x9cinterestingxe2x80x9d activity has occurred and been recorded, it is necessary to move through all the images in their sequence of recording. That is, the sequence of recorded images stored in a memory is queued into a computer display input. The operator then pushes a PLAY button and the computer serially sequences through the stored images. The operator must watch all the images until one is reached that has activity of interest. The present invention solves this problem by a method that allows recorded video to be rapidly scanned with the scanning stopping only at those images where a change in the activity recorded exceeds a predetermined threshold.
Among the several objects of the present invention may be noted the provision of a method of scanning recorded video images of a scene to rapidly locate those images in which there is a predetermined amount of activity. The method involves first obtaining images of a scene over a period of time. One of the images is designated a reference image of the scene and the other images are compared to this reference one at a time. The reference image is periodically updated as conditions warrant. A difference image is created for each comparison of an image to the reference image, and the difference images are stored in a memory of the system. A threshold test is applied to each difference image as a measure of the activity occurring in the scene at the time the image is obtained and the results of the test are stored with the image. When the images are to be subsequently viewed, a viewing threshold related to the amount of activity occurring in the scene is established by the viewer. Information stored with each image is then scanned to determine which images meet the viewing criteria. Those images that do are either displayed, in time sequence, for viewing or used to create a separate file for analysis. Since the viewing threshold criteria can be rapidly determined for a large number of stored images, it is not necessary to view the images in their sequential order which saves a substantial amount of time and allows the user to quickly locate pertinent information related to activities at a monitored site. Other objects and features will be in part apparent and in part pointed out hereinafter.